Fringed bat COSEWIC assessment and status report: chapter 18

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Appendix 1.  The occurrence of the Fringed Bat (Myotis thysanodes) in coastal Washington

Background

Most distribution maps (e.g., O’Farrell and Studier 1980; Hall 1981) show the Fringed Bat occurring east of the Cascade Mountains north of Columbia River with populations in Washington and British Columbia restricted to arid intermontane grasslands. The Washington records summarized by Johnson and Cassidy (1997) show no coastal occurrences. However, Barbour and Davis (1969) and Manning (1993) noted the occurrence of this species in coastal Washington but gave no actual location records. The only known coastal record for Washington is a specimen collected in 1940 near Quinault Lake in Olympic National Park on the Olympic Peninsula reputedly identified as M. thysanodes by Scheffer (1995). The Olympic Peninsula location is in the humid rainforest region of Washington. Although Scheffer (1995) reported the specimen as being deposited in the Olympic Park museum, the museum has no bat specimens. A search of North American museums collections revealed that the specimen was deposited in the collections of the Museum of Vertebrate Zoology (MVZ), University of California, Berkeley. It was identified as the Little Brown Bat (Myotis lucifugus) and catalogued as MVZ 181447. I arranged a loan of the specimen through MVZ and the Royal British Columbia Museum.

Identification

MVZ 181447 is a skin and skull with part of the forearms removed. Body measurements (recorded on specimen tag) are total length=75 mm, tail vertebrae= 35 mm, hind foot= 6 mm, ear=15 mm, tragus=10 mm, and forearm length= 36 mm. From the long ears, pronounced fringe of hairs on the edge of the interfemoral membrane, steeply sloped forehead, and the ratio of the interorbital width/maxillary toothrow length= 0.66, the specimen is clearly a member of the long-eared myotis group and not Myotis lucifugus. Except for skull length, the skull measurements fall within the size range of the small coastal subspecies M. t. vespertinus found in Oregon and California. Some of the dental measurements and the shorter skull length are consistent with measurements given by van Zyll de Jong and Nagorsen (1994) for the Western Long-eared Myotis (Myotis evotis) and Keen’s Long-eared Myotis (Myotis keenii). In external features the specimen has smaller ears than M. keenii and M. evotis and has a prominent fringe of stiff hairs (1.5 mm length) on edge of the interfemoral membrane that extend from the tail to an area mid-point with the hind foot, a characteristic of the coastal form M. t. vespertinusdescribed by Manning and Jones (1988). Although M. evotis and M. keenii have hairs on the interfemoral membrane, they are sparse and short (~1 mm).

Conclusions

Misidentified as Myotis lucifugus, MVZ 181447 is a peculiar specimen that shows characteristics of the small coastal subspecies of M. thysanodes (M. t. vespertinus) and characteristics of M. keenii. The prominent fringe of hairs on the interfemoral membrane is consistent with M. thysanodes. I tentatively identify the specimen as M. thysanodes. A tissue sample taken from a wing membrane should be analyzed to determine if a mtDNA sequence can be obtained to verify the identification.

The occurrence of M. thysanodes on the west coast of the Olympic Peninsula in the humid temperate rain forest raises the possibility of a coastal population in south-western British Columbia.